COPEPODA. 



401 



their further growth are connected with a number of suc- 

 cessive moults, and consist principally in an elongation of the 

 body and the appearance of fresh appendages. In the next 

 larval stage (metanauplius, Fig. 262, 

 b), a fourth pair of appendages, the 

 future first maxillae, makes its ap- 

 pearance behind the three original 

 pairs, which develop into the an- 

 tennae and mandibles. In a later 

 stage four fresh pairs of appendages 

 are formed (Fig. 263). Of these the first and 

 second correspond to the second maxillae 

 and maxillipeds, while the third and fourth 

 represent the first rudiments of the an- 

 terior swimming feet. The functional 

 limbs still resemble those of a nauplius, 

 and it is after another moult that the 

 transformation into the first Cyclops-like 

 form occurs. It then resembles the 

 adult animal in the structure of the an- 

 tennae and mouth parts, although the 

 number of the appendages and of the body 

 rings is still incomplete (Fig. 262, c). 

 The last two pah's of appendages already 

 have the form of short biramous swimming 

 feet, and the rudiments of the third and FJ( J. 263. Metanaupiius of 

 fourth pairs of swimming feet have made 



their appearance as projections beset with tlree n an^oY Swimming 

 setae.* The body consists in this stage of ^ SS^e^nTi 

 the oval cephalothorax ; of the second, third ^-"^'^mandibiet" 



and fourth thoranin qpcrmpnt anrl nf an Mz', J/*" first and second 



Segments , ana OI an maxiUae ; Mx.p maxilli- 



elongated terminal portion, which gives dagej aiS After r aauf Ppen " 

 rise to the last thoracic segment and to 



all the abdominal segments by progressive segmentation. It 

 already terminates in the caudal fork. 



Many forms of parasitic Copepoda, for example Lernanthropus 

 and Chondracanthus (Fig. 265), do not get beyond this stage of 

 body segmentation, and obtain neither the swimming feet of the 



* Hartog finds that the setae are formed inverted, and that they 

 become everted when a larval skin is shed. 



Z III D D 



